DESC:FIELD
The present disclosure relates to aromatic sulfone polymer.
BACKGROUND
Aromatic sulfone polymers belong to the family of thermoplastic polymers. Aromatic sulfone polymer is linear, amorphous, and moldable polymer possessing a number of desirable features such as high glass transition temperature, good thermal stability at high temperatures, good electrical properties, and toughness. Due to these properties, the aromatic sulfone polymer is useful for a variety of applications including consumer goods, machine parts, medical equipment, and packaging and storing materials. The aromatic sulfone polymer can be used to manufacture a variety of useful articles, such as molded articles, films, sheets fibers, and the like.
Further, aromatic sulfone polymers offer high chemical resistance and are particularly useful for manufacturing articles that are exposed to chemicals at elevated temperatures and for extended time period. For example, aromatic sulfone polymers find application in the manufacture of articles such as medical trays, which are subjected to repeated and severe sterilization processes.
Aromatic sulfone polymers used for these applications have high molecular weight. Some of these desirable properties of the aromatic sulfone polymers can be further improved by cross-linking.
Conventional processes for preparing the aromatic sulfone polymer have certain limitations. Art continues to develop processes for preparation of aromatic sulfone polymer having desired range of requisite properties such as molecular weight and glass transition temperature.
There is, therefore, felt a need to provide a process for preparation of aromatic sulfone polymers having desired properties. Further, there is need for a simple process for cross-linking the aromatic sulfone polymers.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for a simple process for preparing aromatic sulfone polymers.
Yet another object of the present disclosure is to provide a process for preparing aromatic sulfone polymers having desired physical properties.
Still another object of the present disclosure is to provide a process for a simple process for cross-linking the aromatic sulfone polymers.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In one aspect, the present disclosure provides a process for preparing an aromatic sulfone polymer having inherent viscosity in the range from 0.1 to 0.8 dL/g. The process of the present disclosure comprises polymerizing a monomer mixture containing equimolar amounts 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base in at least one first fluid medium. The ratio of the amount of the monomer mixture and the amount of the first fluid medium ranges from 1:100 and 7:100 on mass basis.
The process for preparing an aromatic sulfone polymer in accordance with the process of the present disclosure comprises the following steps:
The monomer mixture and the first base are admixed with the first fluid medium to obtain a reaction mixture.
The reaction mixture is heated with continuous removal of water. This step is followed by further heating at a temperature in the range of 150°C to 200°C for 10 to 20 hours to obtain a product mixture containing the aromatic sulfone polymer.
The product mixture is cooled and the cooled product mixture is added to a mixture of water and methanol. This step is followed by neutralizing and filtering to obtain a residue containing the aromatic sulfone polymer. The residue is purified and dried to obtain the aromatic sulfone polymer.
The first fluid medium is at least one selected from the group consisting of dimethyl sulfoxide (DMSO) and toluene.
In accordance with one embodiment of the present disclosure, the first fluid medium is a mixture of dimethyl sulfoxide (DMSO) and toluene.
The first base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.
In accordance with the embodiments of the present disclosure, the product mixture is cooled to a temperature in the range of 50 °C to 90 °C.
In accordance with the embodiments of the present disclosure, the step of drying is carried out at a temperature in the range of 40 °C to 80 °C for a time period ranging from 10 hours to 15 hours.
In the second aspect, the present disclosure provides an aromatic sulfone polymer having inherent viscosity in the range from 0.1 to 0.8 dL/g obtained by polymerizing a monomer mixture containing equimolar amounts of 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base and at least one first fluid medium. The ratio of the amount of the monomer mixture and the first fluid medium is in the range of 1:100 and 7:100 on mass basis.
The glass transition (Tg) temperature of the aromatic sulfone polymer obtained by the process of the present disclosure ranges from 160 °C to 200 °C.
In the third aspect, the present disclosure provides a process for preparing cross-linked aromatic sulfone polymer. The process involves the following steps:
The aromatic sulfone polymer is chlorinated using at least one chlorinating agent in at least one second fluid medium to obtain chlorinated aromatic sulfone polymer.
The chlorinated aromatic sulfone polymer is cross-linked using at least one cross-linking agent and at least one second base in at least one third fluid medium to obtain a cross-linked aromatic sulfone polymer.
The chlorinating agent is at least one selected from the group consisting of benzoyl chloride and acetyl chloride. Chlorination of the aromatic sulfone polymer is carried out in the presence of zinc chloride as a catalyst.
The second fluid medium is at least one selected from the group consisting of dichloromethane, methanol and chlorobenzene.
In accordance with the embodiments of the present disclosure, the second fluid medium is a mixture of dichloromethane, methanol and chlorobenzene.
The cross-linking agent is at least one selected from the group consisting of hydroquinone, 4,4’-bisphenol and phenelyne-1,4-diisopropylidene bisphenol.
The third fluid medium is at least one selected from the group consisting of dimethyl sulfoxide (DMSO).
The second base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.
In accordance with the embodiments of the present disclosure, the aromatic sulfone polymer produced is a high molecular weight polymer that possesses high thermal stability, toughness, and high glass transition temperature (Tg).
In accordance with the present disclosure, cross-linking of the aromatic sulfone polymer improves the following properties of the aromatic sulfone polymer tracking resistance, fluid medium resistance and weathering properties.
The physical properties of the aromatic sulfone polymer can be tuned by varying the concentration of the monomers.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The process of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a plot of inherent viscosity (IV) of aromatic sulfone polymer versus the concentration of the monomers in accordance with the present disclosure;
Figure 2 illustrates a thermo gravimetric analysis (TGA) of an aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 3 illustrates a differential scanning calorimetric (DSC) analysis of the aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 4 illustrates a Fourier Transform Infrared (FT-IR) spectrum of the aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 5 illustrates solid state 13C-NMR spectra of the aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 6 illustrates UV spectra of the aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 7 illustrates a wide angle X-ray diffraction of the aromatic sulfone polymer prepared in accordance with the present disclosure;
Figure 8a, 8b, 8c and 8d illustrate solid state 13C-NMR spectra of a halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the present disclosure;
Figure 9 illustrates thermo gravimetric analysis (TGA) of the halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the present disclosure; and
Figure 10 illustrates a differential scanning calorimetric (DSC) analysis of the aromatic sulfone polymer, halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the present disclosure.

DETAILED DESCRIPTION
There is a need for a process for preparation of aromatic sulfone polymers having desired properties. The present disclosure envisages a process for preparing aromatic sulfone polymers having desired molecular weight by varying the initial monomer concentration. In the process of the present disclosure, properties of the aromatic sulfone polymer such as molecular weight and glass transition temperature are found to depend upon the initial monomer concentration of the mixture subjected to polymerization.
In a first aspect of the present disclosure, there is provided a process for preparing an aromatic sulfone polymer having inherent viscosity in the range from 0.1 to 0.8 dL/g. The process comprises polymerizing a monomer mixture comprising equimolar amount of 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base in at least one first fluid medium. The ratio of the amount of the monomer mixture and the first fluid medium is in the range of 1:100 and 7:100 on mass basis.
The process for the preparing the aromatic sulfone polymer involves the following steps:
The monomer mixture and the first base are admixed with the first fluid medium to obtain a reaction mixture.
The reaction mixture is heated with continuous removal of water. This step is followed by further heating at a temperature in the range of 150°C to 200°C for 10 to 20 hours to obtain a product mixture containing the aromatic sulfone polymer.
The product mixture is cooled, and the cooled product mixture is added to a mixture of water and methanol. This step is followed by neutralizing and filtering to obtain a residue containing the aromatic sulfone polymer. The residue is purified and dried to obtain the aromatic sulfone polymer.
The first fluid medium used for the polymerization is at least one selected from the group consisting of dimethyl sulfoxide (DMSO) and toluene.
In accordance with one embodiment of the present disclosure, the first fluid medium is a 1:1 v/v mixture of dimethyl sulfoxide (DMSO) and toluene.
The first base used for the polymerization is selected from the group consisting of alkali metal carbonates and alkali metal hydroxides.
In accordance with the embodiments of the present disclosure, the first base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.
In accordance with one embodiment of the present disclosure, the first base used for polymerization is potassium carbonate.
In accordance with one embodiment of the present disclosure, the continuous removal of water during the process of the present disclosure is carried out by azeotropic distillation.
In accordance with one embodiment of the present disclosure, the neutralization is carried out using glacial acetic acid.
In accordance with one embodiment of the present disclosure, the residue containing the aromatic sulfone polymer is purified by:
a) washing the precipitate with methanol to remove extraneous organic matter; and
b) heating the washed precipitate in water for a time period ranging from 1 hour to 2 hours; and further heating the precipitate in methanol for a time period ranging from 1 hour to 2 hours to remove any trapped inorganic salt and fluid mediums from the precipitate.
In accordance with one embodiment of the present disclosure, the product mixture is cooled to a temperature in the range of 50 °C to 90 °C.
In accordance with one embodiment of the present disclosure, the step of drying is carried out at a temperature in the range of 40 °C to 80 °.
In the second aspect, the present disclosure provides aromatic sulfone polymer having inherent viscosity in the range from 0.1 to 0.8 dL/g obtained by polymerizing a monomer mixture containing equimolar amounts of 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base and at least one first fluid medium. The ratio of the amount of the monomer mixture and the first fluid medium is in the range of 1:100 and 7:100 on mass basis.
In accordance with the embodiments of the present disclosure, the glass transition temperature of the aromatic sulfone polymer ranges from 160 °C to 200 °C.
In the third aspect, the present disclosure provides a process for preparing cross-linked aromatic sulfone polymer. The process of preparing cross-linked aromatic sulfone polymer involves the following steps:
The aromatic sulfone polymer is chlorinated using at least one chlorinating agent in at least one second fluid medium to obtain chlorinated aromatic sulfone polymer.
The chlorinated aromatic sulfone polymer is cross-linked using at least one cross-linking agent and at least one second base in at least one third fluid medium to obtain a cross-linked aromatic sulfone polymer.
The chlorinating agent is at least one selected from the group consisting of benzoyl chloride and acetyl chloride.
The chlorination of the aromatic sulfone polymer is carried out in the presence of a catalyst.
In accordance with one embodiment of the present disclosure, the catalyst is zinc chloride.
The cross-linking agent is an aromatic compound having two hydroxyl groups.
In accordance with the embodiments of the present disclosure, the cross-linking agent is at least one selected from the group consisting of hydroquinone, 4,4’-bisphenol and phenelyne-1,4-diisopropylidene bisphenol.
The second base used for cross-linking step is selected from the group consisting of alkali metal carbonates and alkali metal hydroxides.
The second base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.
In accordance with one embodiment of the present disclosure, the second base is potassium carbonate.
It is observed that a high molecular weight aromatic sulfone polymer is obtained by the process of the present disclosure. Further, the intrinsic viscocity (IV) and molecular weight of the aromatic sulfone polymers increases with increasing initial monomer concentration. An aromatic sulfone polymer having desired molecular weight can be obtained by using requisite initial monomer concentration.
The aromatic sulfone polymer of the present disclosure has following properties:
• good thermal stability;
• good electrical properties;
• toughness; and
• high glass transition temperature (Tg).
It is observed that the molecular weight, the thermal stability, and the glass transition temperature (Tg) of the aromatic sulfone polymers increase by increasing the concentration of the monomers. It is also observed that due to high molecular weight, the thermal stability and the glass transition temperature (Tg) of the cross-linked polymer increases.
Further, it is observed that, on cross-linking the aromatic sulfone polymers, properties of the aromatic sulfone polymers such as tracking resistance, fluid medium resistance, weathering properties, and the like, can be improved.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experiment:
Experiment 1: Preparation of aromatic sulfone polymer
The aromatic sulfone polymer was prepared by varying the concentration of a monomer mixture in a first fluid medium.
In a reaction vessel equipped with a Dean-Stark trap, a condenser, a nitrogen inlet, and a thermometer, were charged 4,4’-dihydroxydiphenylsulfone (DHDPS), 4,4’-dichlorodiphenylsulfone (DCDPS) and potassium carbonate in the molar ratio of 1:1:1.3. Dimethyl sulfoxide (DMSO) and toluene were added to the reactor to obtain a reaction mass. The entire operation was conducted under constant nitrogen purging.
The reactant mass was heated with continuous stirring until toluene began to reflux, and then heated under reflux for 10 hours. During this period, water was continuously removed by azeotropic distillation. The temperature was further raised to 170°C and maintained for 12 hours. The reaction was then allowed to continue for an additional 3 hours at 175°C.
The reaction mixture was then cooled to 80ºC, and was poured into 1:1 mixture of water and methanol (V/V). This resultant mixture was neutralized with glacial acetic acid. Precipitated polymer was collected by filtration and washed with methanol. Further, the washed polymer was mixed with water and heated at 100°C for 1 hour followed by separating and repeating the same procedure with methanol. The water wash and methanol wash at higher temperature removed trapped inorganic salt and fluid media from the polymer. The polymer was dried in a vacuum oven at 60°C for 12 hours.
The results of the synthesis of the aromatic sulfone polymer using various monomer concentrations are provided in Table 1.
Table 1: Yield of the aromatic sulfone polymer
Monomer Concentrations (%) DHDPS (mmol) DCDPS (mmol) First Fluid medium Potassium carbonate
(mmol) Yield (%)
DMSO (mL) Toluene (mL)
1 2.0 2.0 50 50 2.4 54
2 3.8 3.8 50 50 5.1 54.9
3 5.7 5.7 50 50 7.5 78.82
4 7.7 7.7 50 50 9.7 83.77
5 9.8 9.8 50 50 12.3 81.94
6 11.9 11.9 50 50 14.9 86.03
7 14.2 14.2 50 50 17.6 81.11
It is observed that higher yield of the aromatic sulfone polymer is obtained at higher monomer concentration.
Experiment 2: Chlorination of aromatic sulfone polymer
To a reactor equipped with a mechanical stirrer, a condenser and a dropping funnel, were charged dichloromethane and methanol in a ratio of 30:1 (w/w) followed by cooling to -2 °C and addition of benzoyl chloride in a drop-wise manner. The resultant mixture was diluted with chlorobenzene, and Zinc chloride was added to the diluted mixture. The aromatic sulfone polymer prepared in Experiment 1 was added to the resulting mixture to obtain a reaction mixture. The reaction mixture was heated for 8 hours.
After 8 hours of heating, the reaction mixture was quenched with water. The volume of the mixture was reduced to 50 mL followed by addition to methanol to obtain a precipitate of chlorinated aromatic sulfone polymer. The chlorinated aromatic sulfone polymer was further purified by re-precipitation in methanol. The precipitate was finally dried at 120°C.
Yield (%) of halogenated aromatic sulfone polymer prepared by varying amounts of benzoyl chloride are presented in Table 2.
Table 2: Preparation of halogenated of aromatic sulfone polymer using benzoyl chloride
Aromatic sulfone polymers (mol) Benzoyl chloride (mol) Zinc chloride (mol) DCM* (mol) Methanol (mL) Chloro-benzene (mL) Yield (%) of halogenated aromatic sulfone polymer
0.022 0.40 0.0031 0.53 2 187 35
0.022 0.47 0.0026 0.53 2 187 59
0.022 0.51 0.0021 0.53 2 187 25
DCM* = Dichloromethane
It is evident from Table 2 that the yield of chlorinated aromatic sulfone polymer depends upon the amounts of benzoyl chloride and zinc chloride.
The process described herein-above for chlorination of aromatic sulfone polymer was carried out using acetyl chloride as halogenating agent instead of benzoyl chloride. The yield of the chlorinated aromatic sulfone polymer increased when acetyl chloride is used as a chlorinating agent instead of benzoyl chloride. Table 3 summarizes the chlorination of aromatic sulfone polymer by acetyl chloride.
Table 3: Preparation of halogenated aromatic sulfone polymer using acetyl chloride
Aromatic sulfone polymers (mol) Acetyl chloride (mol) Zinc chloride (mol) DCM (mol) Methanol (mL) Chloro-benzene (mL) Yield (%) of halogenated aromatic sulfone polymer
0.022 0.49 0.0031 0.53 2 187 87
DCM* = Dichloromethane

Experiment 3: Cross-linking the halogenated aromatic sulfone polymer (obtained in Experiment 2)
The halogenated aromatic sulfone polymer was cross-linked with the help of cross-linking agents provided in Table 4.

Table 4: List of cross-linking agents
Cross-linking agent 1 Hydroquinone

Cross-linking agent 2 4,4’- bisphenol

Cross-linking agent 3 Phenelyne-1,4-diisopropylidene bisphenol

The halogenated aromatic sulfone polymer obtained in Experiment 2, at least one cross-linking agent, potassium carbonate and dimethyl sulfoxide (DMSO) were added in a reactor to obtain a reaction mixture. The reaction mixture was heated at 120°C for 1 hour, while stirring. The reaction mixture was further heated to 165°C for 5 hours, while stirring. The reaction mixture was poured in a mixture of water and methanol (1:1 v/v) and the resultant mixture neutralized with acetic acid followed by filtering. The precipitate was dried under reduced pressure at 80°C. The experimental details are provided in Table 5.

Table 5: Experimental details for cross-linking the chlorinated aromatic sulfone polymer
Halogenated aromatic sulfone (mmol) Cross-linking agent (mmol) Base (mmol) DMSO (mL)
1.2 Cross-linking agent 1 (0.6) 1.6 5
2.1 Cross-linking agent 2 (1.07) 2.6 5
2.1 Cross-linking agent 3 (0.9) 2.6 5

Characterization of the aromatic sulfone polymer
Inherent viscosity (IV)
The inherent viscosity (IV) of the aromatic sulfone polymer prepared by the procedure mentioned in Experiment 1 was measured in the form of an N-methyl-2-pyrrolidone (NMP) solution (concentration of the aromatic sulfone polymer in NMP was 0.2g/dL) at 30ºC in a constant temperature water bath using a Cannon Model Ubbelohde Capillary Dilution Viscometer. The IV values of the aromatic sulfone polymers were obtained by flow time data and the results are shown in Figure 1.
Figure 1 illustrates a plot of inherent viscosity (IV) of aromatic sulfone polymers versus their initial monomer concentration. IV values indicated in Figure 1 are tabulated herein below in Table 6.
Table 6: IV values of the aromatic sulfone polymer
Initial monomer concentration (weight %) Inherent viscosity (IV)
1 0.23
2 0.25
3 0.34
4 0.37
5 0.39
6 0.50
7 0.61

From Figure 1 and Table 6 it is clear that the IV of the aromatic sulfone polymers increases with increasing the initial monomer concentration.
The inherent viscosity (IV) of aromatic sulfone polymer corresponds to its molecular weight. Thus, the molecular weight of the aromatic sulfone polymer increases with increasing initial monomer concentration.
Hence, from Figure 1 and Table 6, it can be concluded that aromatic sulfone polymers having desired molecular weight can be obtained by using requisite initial monomer concentration.

Thermal stability
The thermal stability of the aromatic sulfone polymers prepared by the procedure mentioned in Experiment 1 was evaluated and the results are summarized in Table 7.
Table 7: Thermal stability of the aromatic sulfone polymers
Initial monomer concentration (%) Temperature (ºC) for 10% loss in weight Weight (%) remaining at 250ºC Weight % remaining at 750ºC
1 155 75 9
2 175 76 11
3 195 80 16
4 212 87 18
5 233 89 35
6 255 90 26
7 449 96 43

From table 7, it is observed that the temperature for 10% weight loss increases with increasing molecular weight of the aromatic sulfone polymer. The weight (%) remaining at 750 ºC is higher for the higher molecular weight polymer. The increased thermal stability for the high molecular weight polymer is due to the fact that the high molecular weight polymer chain needs higher temperature for degradation.
Hence, the aromatic sulfone polymer prepared using 7 weight% initial monomer concentration has high thermal stability.
Figure 2 illustrates a thermo gravimetric analysis (TGA) of the aromatic sulfone polymer prepared using 7 weight% initial monomer concentration. The aromatic sulfone polymer sample was subjected to exhaustive drying in a vacuum oven at 100 ºC before TGA. A distinct weight loss can be observed in Figure 2 around 500 ºC to 600 ºC due to the degradation of the polymer backbone.
Glass transition temperature (Tg)
The glass transition temperature of the aromatic sulfone polymers prepared by the procedure mentioned in Experiment 1 was measured and the results are shown in Table 8. The glass transition temperature (Tg) was determined in a temperature range of 30ºC to 350ºC and at a scan rate of 10 ºC /min by DSC.

Table 8: Glass transition temperature (Tg) for the aromatic sulfone polymers
Initial monomer concentration (weight %) Glass Transition temperature (Tg) (ºC)
1 167.57
2 167.80
3 174.58
4 176.21
5 174.71
6 177.09
7 192.62

It is observed from Table 8 that with an increase in the initial monomer concentration from 1 weight% to 7 weight%, the glass transition temperature (Tg) of the aromatic sulfore polymer increases from 167.57 ºC to 192.62 ºC. Thus, the Tg of the aromatic sulfore polymer increases with increase in initial monomer concentration.
Figure 3 illustrates a differential scanning calorimetric (DSC) analysis of the aromatic sulfone polymer prepared using 7 weight% initial monomer concentration.

Spectral analysis
The aromatic sulfone polymers prepared by the process as described in Experiment 1, were analyzed by spectroscopic techniques such as Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), and Ultra-violet (UV).
Figure 4 illustrates a FT-IR spectrum of the aromatic sulfone polymer prepared using the initial monomer concentration of 7 weight% in accordance with the present disclosure. A representative FT-IR spectrum is shown in Figure 4. The absorption band at 1103 cm-1 and 1149 cm-1 is characteristic of the ether linkage, indicating the formation of the polymer of the present disclosure.
Figure 5 illustrates a solid state 13C-NMR spectrum of the aromatic sulfone polymer prepared using the initial monomer concentration of 7 weight% in accordance with the present disclosure.
Figure 6 illustrates UV spectra of the aromatic sulfone polymer prepared in accordance with the present disclosure. The aromatic sulfone polymers obtained by varying the initial monomer concentration from 1 weight% to 7 weight% were analyzed. The UV absorption of aromatic sulfone polymer having different IV was studied in the form of dilute solutions in N-Methylpyrrolidone (NMP) (0.2g/dL).
The electronic absorption spectra of both the solid and solution are presented in Figure 6. UV spectra of the aromatic sulfone polymer obtained by varying the initial monomer concentration from 1 weight% to 7 weight% are represented by the curves a1 to a7. These UV spectra indicated one distinct peak at higher wavelength absorption around 320 nm (indicated by vertical line A). The absorption maxima at around 320 nm corresponds with the p–p* transition of the aromatic sulfone polymers. Another transition at around 420 nm (indicated by vertical line B) is due to the n-p* transition.

X-ray diffraction
The aromatic sulfone polymers prepared by the procedure mentioned in Experiment 1 were analyzed by X-ray diffraction technique to identify the crystallinity of the aromatic sulfone polymers.
Figure 7 illustrates a wide angle X-ray diffraction pattern of the aromatic sulfone polymer prepared using the initial monomer concentration of 7 weight%. It is evident that the aromatic sulfone polymer prepared with 7 weight% initial monomer concentration in accordance with the process of the present disclosure is amorphous in nature.
Characterization of halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymer:
The halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymer prepared from the process described in Experiment 2 and Experiment 3 were analyzed by Nuclear Magnetic Resonance (NMR). The results obtained from the NMR analysis are illustrated in the following Figures 8a, 8b, 8c and 8d.
Figures 8a, 8b, 8c and 8d illustrate solid state 13C NMR spectra of the halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the present disclosure. Figure 8a corresponds to the halogenated aromatic sulfone polymer. Figures 8b, 8c and 8d correspond to cross-linked aromatic sulfone polymers by utilizing cross-linking agent 1, cross-linking agent 2 and cross-linking agent 3, respectively.
Thermal Stability
The thermal stability of the halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared by the process mentioned in Experiment 2 and Experiment 3 were analyzed and the results are shown in Figure 9.
Figure 9 illustrates thermo gravimetric analysis (TGA) of the halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the process of the present disclosure. Figure 9 illustrates weight loss (%) of the halogenated aromatic sulfone polymer (indicated by A) and cross-linked aromatic sulfone polymers (indicated by 1, 2 and 3). It is evident from Figure 9 that, the weight remaining in percentage of halogenated aromatic sulfone polymer was less as compared to cross-linked sulfone polymers. This is due to high molecular weight of cross-linked sulfone polymers which gives higher thermal stability to the cross-linked sulfone polymers. Due to higher thermal stability of the cross-linked sulfone polymers, higher temperature is required for degradation.
Glass transition temperature (Tg)
The glass transition temperatures of the halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared by the procedure mentioned in Experiment 2 and Experiment 3 were analyzed and the results are shown in Figure 10.
Figure 10 illustrates a differential scanning calorimetric (DSC) analysis of the aromatic sulfone polymer, halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers prepared in accordance with the present disclosure. The glass transition temperature (Tg) of the aromatic sulfone polymer, halogenated aromatic sulfone polymer and cross-linked aromatic sulfone polymers was determined by DSC. The Tg values of aromatic sulfone polymer (indicated by A0), halogenated sulfone polymer (indicated by A) and cross-linked aromatic sulfone polymers (indicated by 1, 2 and 3) are shown in Figure 10. The Tg of cross-linked aromatic sulfone polymers was found to be greater than halogenated sulfone polymer and aromatic sulfone polymers.
From Figure 10 it is evident that with an increase in molecular weight of the polymers, the glass transition temperature (Tg) and the thermal stability of the polymer increases.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? aromatic sulfone polymers having desired intrinsic viscosity or desired molecular weight using requisite initial monomer concentration in the polymerization mixture;
? aromatic sulfone polymers having desired thermal stability and/or desired glass transition temperature (Tg) using requisite initial monomer concentration in the polymerization mixture;
? amorphous aromatic sulfone polymers; and
? improved properties such as tracking resistance, fluid medium resistance and weathering properties by cross-linking the aromatic sulfone polymer.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:1. A process for preparing an aromatic sulfone polymer having inherent viscosity in the range of 0.1 to 0.8 dL/g, said process comprises polymerizing a monomer mixture containing equimolar amounts 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base in at least one first fluid medium, wherein the ratio of the amount of said monomer mixture and the amount of said first fluid medium is in the range of 1:100 and 7:100 on mass basis.
2. The process as claimed in claim 1 comprising the following steps:
a) admixing said monomer mixture and said first base with said first fluid medium to obtain a reaction mixture;
b) heating said reaction mixture with continuous removal of water, followed by further heating at a temperature in the range of 150°C to 200°C for 10 to 20 hours to obtain a product mixture containing the aromatic sulfone polymer;
c) cooling said product mixture and adding the cooled product mixture to a mixture of water and methanol, followed by neutralizing and filtering to obtain a residue containing the aromatic sulfone polymer; and
d) purifying said residue and drying to obtain the aromatic sulfone polymer.
3. The process as claimed in claim 1 or claim 2, wherein said first fluid medium is at least one selected from the group consisting of dimethyl sulfoxide (DMSO) and toluene.
4. The process as claimed in claim 1 or claim 2, wherein said first fluid medium is a mixture of dimethyl sulfoxide (DMSO) and toluene.
5. The process as claimed in claim 1 or claim 2, wherein said first base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.
6. The process as claimed in claim 2, wherein said product mixture is cooled to a temperature in the range of 50 °C to 90 °C.
7. The process as claimed in claim 2, wherein said step of drying is carried out at a temperature in the range of 40 °C to 80 °C for a time period ranging from 10 hours to 15 hours.
8. An aromatic sulfone polymer having inherent viscosity in the range of 0.1 to 0.8 dL/g obtained by polymerizing a monomer mixture containing equimolar amounts of 4,4’-dihydroxydiphenylsulfone (DHDPS) and 4,4’-dichlorodiphenylsulfone (DCDPS) using at least one first base and at least one first fluid medium, wherein the ratio of the amount of said monomer mixture and said first fluid medium is in the range of 1:100 and 7:100 on mass basis.
9. The aromatic sulfone polymer as claimed in claim 8, wherein the glass transition temperature of the aromatic sulfone polymer ranges from 160 °C to 200 °C.
10. A process for preparing cross-linked aromatic sulfone polymer, said process comprising the following steps:
a) chlorinating aromatic sulfone polymer using at least one chlorinating agent in at least one second fluid medium to obtain chlorinated aromatic sulfone polymer; and
b) cross-linking said chlorinated aromatic sulfone polymer using at least one cross-linking agent and at least one second base in at least one third fluid medium to obtain a cross-linked aromatic sulfone polymer.
11. The process as claimed in claim 10, wherein said chlorinating agent is at least one selected from the group consisting of benzoyl chloride and acetyl chloride.
12. The process as claimed in claim 10, wherein chlorination of the aromatic sulfone polymer is carried out in the presence of zinc chloride as a catalyst.
13. The process as claimed in claim 10, wherein said second fluid medium is at least one selected from the group consisting of dichloromethane, methanol, and chlorobenzene.
14. The process as claimed in claim 10, wherein said cross-linking agent is at least one selected from the group consisting of hydroquinone, 4,4’-bisphenol, and phenelyne-1,4-diisopropylidene bisphenol.
15. The process as claimed in claim 10, wherein said third fluid medium is dimethyl sulfoxide (DMSO).
16. The process as claimed in claim 10, wherein said second base is at least one selected from the group consisting of potassium carbonate, sodium carbonate, and cesium carbonate.